1. Field of the Invention
The embodiments of the present invention relate generally to a filter housing assembly.
2. Background of the Invention
Clean rooms are utilized in many industries for contamination control and to improve product yields. A plurality of filters, typically mounted in the ceiling of the cleanroom, are configured to remove particulate from air entering the cleanroom at a predetermined efficiency selected based upon the cleanliness requirements of the activities performed in the cleanroom. As particulates load the filtration media disposed in the filter, the airflow through the filter decreases as the pressure drop across the filter increases. Once the filter reaches a critical pressure drop, the filter is typically replaced.
In other applications, replacement of filters is scheduled based on time or processes performed within the cleanroom. For example, in many pharmaceutical and biotech clean rooms, periodic replacement of filters is required to meet regulatory or owner specifications. To facilitate efficient replacement of the filter, a hood (housing) is typically mounted in the cleanroom ceiling in which the filter may be readily removed and replaced.
Ducted supply hoods with roomside replaceable filters are commonly used in pharmaceutical applications for cleaning supply air to cleanroom manufacturing and process areas, as well as to laboratory areas. Typically, a plurality of supply hoods are coupled to a blower by a duct network. The hoods are supplied with adjustable dampers that allow customers to regulate the airflow without having to remove the filter from the hood. The most common types of dampers are guillotine, opposed blade and butterfly types. Importantly, the dampers allow the air flow through each filter coupled to the duct network to be balanced individually to obtain a desired distribution of air flow entering the room through the various filters.
During operation of the cleanroom, the filter within the filter modules trap particulate and other matter, thereby increasing air flow resistance through the filter. Thus, if one filter requires replacement, the reduced resistance of the replacement filter relative to the other filters coupled to a common ductwork results in an increased airflow through the new filter and a corresponding reduction of air flow in the other filters. This unbalances the airflow distribution into the cleanroom, often to the point of non-conformance to room balancing criteria. To remedy this problem, the supply hoods coupled to the ductwork must be rebalanced.
As balancing the airflow requires accurately making airflow measurements and the damper adjustments over a repetitive cycle at each filter, the man-hours cost of balancing a room is high. Moreover, due to the repetitive nature of airflow measurement gathering and damper adjustment during the balancing procedure, balancing a room undesirably results in lost cleanroom operation time.
Therefore, there is a need for a filter module and method for replacing a filter that reduces the time required to balance airflow between a series of filter modules having a common air source.